1. Field of the Invention
The present invention relates to a technique of recording and playing back a digital image using a digital device having a capability of treating a digital image, such as a digital camera, a scanner, a printer, or a PC (personal computer).
2. Description of the Related Art
The Exif (Exchangeable Image Fie Format) is widely used as a format for use by an image recording apparatus such as a digital camera to record a digital image file. In the Exif format, a main image, a sub image (in the form of a thumbnail image), and image attribute information such as picture-taking information are recorded in a predetermined form.
FIG. 2 shows a data structure of a file in the Exif format. As shown in FIG. 2, image attribute information is described in a directory named IFD in a tree directory structure. In the Exif format, it is allowed for a digital camera maker to describe its own IFD information between MakerNote tags in an Exif IFD area.
For example, Japanese Patent Laid-Open No. 2000-261756 discloses a technique of writing compressed sub image data in a file using MakerNote tags.
It is also known in the art to describe information (print commands), necessary to achieve color matching among devices, using MakerNote tags, thereby making it possible to print a high-quality image. By using print commands, it is possible to make various settings in terms of, for example, “brightness in printing”, “color space”, “contrast”, “color saturation”, “sharpness”, and “memory color”.
As described above, MakerNote tags can be used to describe various kinds of information in a specific area in a file so that the information makes the file more valuable in transferring, evaluating, playing back, and/or printing the image.
Because any maker is allowed to freely describe image attribute information using MakerNote tags in accordance with the definition made by the maker, there is a possibility that different types of image attribute information are described depending on the functions and/or performance of digital cameras, even for digital cameras produced by the same maker. For example, even for digital cameras produced by the same maker, the functions and the performance are improved from one generation to next, and the number of types of image attribute information is increased with increasing improvement in the functions and performance. This results in a great increase in the data size of image attribute information.
In order to support playback of image files produced using old-generation digital cameras, it is required to analyze image attribute information which is no longer used in present-generation digital cameras. This causes an increase in the program size of firmware of digital cameras and related devices.
In particular, supporting of attribute information which is used only in particular limited models of digital cameras causes other models of digital cameras to have to deal with such attribute information. This causes a large load to be imposed on design.
If information associated with know-how possessed by a maker or attribute information indicating a particular characteristic of a particular model of digital camera is described together with image data, other makers can easily know what technology the maker uses. This causes a large risk that the technology is stolen by other makers, although this is convenient for users to record and reuse images.